fifo: fix IAR Warning[Pa082]: undefined behavior: the order of volatile accesses is undefined

HiFiPhile · HiFiPhile · commit 3f0d2668f1ac · 2025-11-25T16:41:30.000+01:00
diff --git a/src/common/tusb_fifo.h b/src/common/tusb_fifo.h
@@ -175,7 +175,9 @@ bool     tu_fifo_full(const tu_fifo_t *f);
 bool     tu_fifo_overflowed(const tu_fifo_t *f);
 
 TU_ATTR_ALWAYS_INLINE static inline bool tu_fifo_empty(const tu_fifo_t *f) {
-  return f->wr_idx == f->rd_idx;
+  uint16_t wr_idx = f->wr_idx;
+  uint16_t rd_idx = f->rd_idx;
+  return wr_idx == rd_idx;
 }
 
 TU_ATTR_ALWAYS_INLINE static inline uint16_t tu_fifo_depth(const tu_fifo_t *f) {

Original file line number	Diff line number	Diff line change
`@@ -175,7 +175,9 @@ bool tu_fifo_full(const tu_fifo_t *f);`
`175`	`175`	`bool tu_fifo_overflowed(const tu_fifo_t *f);`
`176`	`176`
`177`	`177`	`TU_ATTR_ALWAYS_INLINE static inline bool tu_fifo_empty(const tu_fifo_t *f) {`
`178`		`- return f->wr_idx == f->rd_idx;`
	`178`	`+ uint16_t wr_idx = f->wr_idx;`
	`179`	`+ uint16_t rd_idx = f->rd_idx;`
	`180`	`+ return wr_idx == rd_idx;`
`179`	`181`	`}`
`180`	`182`
`181`	`183`	`TU_ATTR_ALWAYS_INLINE static inline uint16_t tu_fifo_depth(const tu_fifo_t *f) {`